Generally, a display device is designed with a display effect of wide viewing angle so as to display images facilitating multi-viewers to watch together. However, sometimes or some occasions, when reading confidential information or inputting a password, the display effect of wide viewing angle would cause the confidential information or password to be peeped and thereby being leaked. In order to satisfy the two different requirements of multi-viewers watching and of processing confidential information in public, a display device with adjustable viewing angle which can be switched between a wide viewing angle mode and a narrow viewing angle mode has gradually become a main stream in the display device market.
Privacy protecting mechanisms in the conventional display devices generally can be classified into several types such as direct addition of privacy filter, backlight source control cooperative with additionally added viewing angle control module, and so on. However, the conventional privacy protecting mechanisms would achieve the privacy protecting effect at the expense of display quality, optical character, thickness and weight, and moreover the viewing angle of a valid user may be limited more or less.
Referring to FIG. 1, when a user is viewing a display device 10, the user usually needs to extend his/her field of vision to left and right sides respectively with certain angles (for example, angles θ1 and θ2), so that the whole display device 10 can completely come into his/her field of vision. However, since the principle of the privacy protecting mechanism is to cause image changes in side-view, the user would suffer from the influence of the privacy protecting mechanism more or less when watching the display device 10 in non-front-view and thereby would watch special images such as mosaic caused by the privacy protecting mechanism in the displayed image, the reading or working smoothness is influenced as a result. As shown in FIG. 1, in the display areas C1 and C2 corresponding to viewing angles greater than 10°, the user may feel image interference patterns caused by the privacy protecting mechanism.
For improving the utilization quality of display device, the designer must give a consideration to both the utilization smoothness of user and the achievement of privacy protecting function.